I'm self-employed since 1996 and did and do this from time to time. And I learned a lot of useful things about both the topic and the different business culture

I'm self-employed since 1996 and did and do this from time to time. And I learned a lot of useful things about both the topic and the different business cultures. And got valueable contacts. I do this especially when I enter a (more or less) new discipline for my next big project. Often I feel my knowledge from lifelong ongoing university education (distant teaching) is not enough and I need a kind of an "internship" to know "how they do it". So my advice is: Be well prepared (know at least the basics so you can get the advanced stuff out of it) and do it only between projects of any kind (development, education, ...) so you're not distracted by parallel duties.